Intracellular delivery is an essential challenge for drug development, as low membrane permeability limits the potential of bioactive macromolecules. Thiol-mediated uptake (TMU), operating via dynamic covalent chemistry between exofacial thiols/disulfides of membrane proteins and thiol-reactive species, has appeared as an efficient way for cytosolic delivery. Inhibition of cell-surface thiol is an essential feature of TMU. In this thesis, new scaffolds for TMU were explored. Carbon-based thiol-reactive moieties were known early on to promote cellular delivery. Here, Michael acceptors were studied to enable and inhibit TMU. Different reactivity of thiol-reactive species correlated with different inhibition activity, however additional interactions, such as halogen bonding, improved inhibitors' performance. Successful cytosolic delivery of fluorophore and protein was performed using Michael acceptor as a transporter. Another scaffold, benzopolysulfane, able to create dynamic networks, significantly exceeded the uptake of other transporters. Studies of polysulfide properties and their interactions with thiols were investigated based on naphthalenediimide-polysulfane scaffold.